The objective of this study is to understand the motion of tractor-semitrailers in accident-prone courses and how to maneuver the vehicle to avoid single vehicle accidents. The motion of tractor-semitrailers is mostly yawing and rolling, and pitching is negligibly small except roll-overs. In roll-overs, the inertia of the tractor generates a tremendous pressure on the sliding surface of the coupler, and consequently, the coupler angle freezes until the rolling motion is over. Different mathematical models were developed for roll-over and other motions of the vehicle. Computed results showed a good agreement with full-scale experiments. With the verified mathematical models, recommendations were made as how to maneuver tractor-semitrailers to avoid jack-knives and roll-overs.